Page No 583:
Question 6:
In a hurdle race, a player has to cross 10 hurdles. The probability that he will clear each hurdle is
. What is the probability that he will knock down fewer than 2 hurdles?
Let p and q respectively be the probabilities that the player will clear and knock down the hurdle.
Let X be the random variable that represents the number of times the player will knock down the hurdle.
Therefore, by binomial distribution, we obtain
P (X = x) = 
P (player knocking down less than 2 hurdles) = P (X < 2)
= P (X = 0) + P (X = 1)
=
